Do you need a totally unique plugin code? Or is it the combination of plugin code and manu code?

This setting needs to be explained much better in the Projucer imo, with what the implications are of just leaving it to be auto-generated. God knows why Steinberg decided that 4 alphanumeric characters would be sufficient, 8 bytes would have given an insane number of combinations which would have meant being extremely unlucky to collide.